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SubjectRe: [pdx86-platform-drivers-x86:review-hans 46/59] kernel/stop_machine.c:638:35: error: call to undeclared function 'cpu_smt_mask'; ISO C99 and later do not support implicit function declarations
From
Hi,

On 5/12/22 11:24, Thomas Gleixner wrote:
> On Thu, May 12 2022 at 09:29, kernel test robot wrote:
>>>> kernel/stop_machine.c:638:35: error: call to undeclared function 'cpu_smt_mask'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>> const struct cpumask *smt_mask = cpu_smt_mask(cpu);
>
> This warning with W=1 is not the worst of the problems.
>
> The build will simply fail for CONFIG_SMP=y && CONFIG_SCHED_SMT=n
> because cpu_smt_mask() cannot be resolved.
>
> The other issue is CONFIG_SMP=n. This will fail to build the IFS driver
> because stop_core_cpuslocked() is not available for SMP=n.

The IFS Kconfig already depends on SMP :

config INTEL_IFS
tristate "Intel In Field Scan"
depends on X86 && 64BIT && SMP
select INTEL_IFS_DEVICE
help
Enable ...


So I don't think we need the non-SMP implementation inside
include/linux/stop_machine.h, we only need the #ifdef you
suggest in kernel/stop_machine.c ?

I think it is best to just squash this into the original
patch, do you agree ?

Regards,

Hans





> Something like the below should work as x86 selects SCHED_SMT when
> SMP=y.
>
> Thanks,
>
> tglx
> ---
> --- a/include/linux/stop_machine.h
> +++ b/include/linux/stop_machine.h
> @@ -156,6 +156,12 @@ static __always_inline int stop_machine_
> }
>
> static __always_inline int
> +stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data)
> +{
> + return stop_machine_cpuslocked(fn, data, NULL);
> +}
> +
> +static __always_inline int
> stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
> {
> return stop_machine_cpuslocked(fn, data, cpus);
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -631,6 +631,7 @@ int stop_machine(cpu_stop_fn_t fn, void
> }
> EXPORT_SYMBOL_GPL(stop_machine);
>
> +#ifdef CONFIG_SCHED_SMT
> int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data)
> {
> const struct cpumask *smt_mask = cpu_smt_mask(cpu);
> @@ -649,6 +650,7 @@ int stop_core_cpuslocked(unsigned int cp
> return stop_cpus(smt_mask, multi_cpu_stop, &msdata);
> }
> EXPORT_SYMBOL_GPL(stop_core_cpuslocked);
> +#endif
>
> /**
> * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU
>
>
>

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